Hello @Pafor,
Unfortunately the information found on the Network-wide > Monitor > Clients page when searching for individual clients that are using sponsored guest is the only place to see this information on Dashboard. The Wireless > Monitor > Splash Logins page only records information for SSIDs configured to use "Sign-on splash" options, which sponsored guest login does not fall under. The introduction for this KB goes over what counts as a "Sign-on splash" and shows an example of what the Wireless > Splash login page looks like when it is active: https://documentation.meraki.com/MR/MR_Splash_Page/Splash_Page_Traffic_Flow_and_Troubleshooting
You can use the Network-wide > Clients page to filter for devices that are online and connected to a sponsored guest SSID (use the first dropdown next to the "Usage and clients" heading to filter for a specific SSID). From there, you can apply another filter to see only online clients (if desired). This will allow you to see client devices that are online and connected to the sponsored guest SSID, which may help more easily locate the information you looking for individual devices. Yes, this will still require selecting each device in turn to find the expiration and who granted access, but if the connected device count is relatively low, applying these filters should allow you to search the list quickly.
Additionally, I would recommend using the "Give your feedback" button on the bottom right corner of any Dashboard page to request that a sponsored guest tracking page be added as a feature to Dashboard.
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